1. Field of the Invention
The present invention relates generally to wireless vehicle tire pressure monitoring and, more particularly, to a system and method for wireless vehicle tire pressure monitoring using low frequency initiation.
2. Background
It is known in the automotive industry to provide for wireless monitoring of vehicle tire parameters, particularly tire pressure. In such tire pressure monitoring systems, tire pressure sensors and radio frequency (RF) transmitters are mounted inside each tire, typically adjacent the inflation valve stem. In each tire, the tire pressure sensed by the tire pressure sensor is transmitted by the transmitter to a receiver/controller located on-board the vehicle. The tire pressure information delivered to the receiver/controller by the RF signals from the transmitters is subsequently conveyed to a vehicle operator or occupant, typically in the form of a display.
To recognize the particular tire location (e.g., front left (FL), front right (FR), rear left (RL), rear right (RR)) associated with an RF signal received from a tire transmitter, such tire pressure monitoring systems are programmed in an initialization or sign-up operation. That is, in order to provide a vehicle operator with information specific to each vehicle tire, programming of the tire pressure monitoring system must be undertaken by a technician or vehicle owner so that each RF signal from a tire transmitter will be associated with a particular tire location.
Current tire pressure monitoring systems use a magnetic reed switch in each tire for such programming. More particularly, after the on-board vehicle/controller is placed into a program, initialization, or sign-up mode, the magnetic reed switch in each tire is activated by a technician or vehicle owner using a magnet. Such activation causes the tire transmitter in the tire to transmit a tire pressure signal to the controller on the vehicle. In that regard, each pressure sensor and/or transmitter has a unique identification code associated therewith, which identification code is transmitted with the tire pressure signal. Using such identification codes, and by following a preselected sequence for activating each magnetic reed switch, the controller associates each tire pressure signal with a particular tire location.
Such operation, however, can create problems when tires are subsequently rotated or changed from their initial locations to new locations, or a vehicle tire is replaced. Each time the vehicle tires are rotated or a tire is replaced, initialization or sign-up must be repeated to ensure that the system continues to operate properly by conveying accurate information, including tire location, to the vehicle operator. This initialization requirement makes tire rotation more complex, and increases the possibility of inaccurate operation of the system.
The tire transmitters used in such tire pressure monitoring systems are typically battery powered. As a result, a transmitter has a limited amount of functioning time before its battery must be replaced. To help conserve battery power, the transmitters typically transmit tire pressure information at short, predetermined time intervals when the vehicle is moving. In addition, once the vehicle has been stationary for a predetermined amount of time, the transmitters may transmit tire pressure information at longer predetermined time intervals.
In any event, where two or more tire transmitters associated with a vehicle transmit tire pressure signals or data simultaneously, data collision can result at the vehicle mounted receiver/controller, which can adversely affect proper operation of the tire pressure monitoring system. Such data collision can also result when multiple vehicles equipped with tire pressure monitoring systems are in proximity, and tire transmitters associated with each vehicle simultaneously transmit tire pressure signals or data which may be received at each vehicle mounted receiver/controller.
Thus, there exists a need for an improved system and method for remote tire pressure monitoring. Such a system and method would use low frequency initiators to trigger or initiate transmission of wireless tire information signals from tire mounted transmitters, thereby providing for automatic identification of tire locations, without the need for initialization or sign-up operations. Such a system and method would also use such low frequency initiators to eliminate data collision and increase tire transmitter battery life, as well as to provide for recharging of tire transmitter batteries.